1. Field of the Invention
The present invention relates to a conveying apparatus and more particularly to a conveying apparatus which conveys workpieces used in assembling, for example, semiconductors.
2. Prior Art
Japanese Patent Application Laid-Open (Kokoku) No. 1-31688 discloses one example of an apparatus for conveying, for example, lead frames. In this apparatus, a plurality of processing devices, such as bonders, of the same type are arranged in a row. A single conveying line is provided so that it is used commonly for the processing devices to and from which workpieces are supplied and discharged.
More specifically, in this apparatus, as shown in FIG. 2, a plurality of wire bonders 1A, 1B, 1C and 1D are installed in a row. A main conveyor 2 is installed in front of these wire bonders 1A through 1D, and the conveyer 2 is used commonly for all the bonders. The conveyor 2 is provided along a feed-guiding device 3 and is driven by a motor 4.
As seen in the bonder 1B, each one of the wire bonders 1A through 1D is provided with a supply means 5 which picks up the workpieces from the main conveyor 2, a pitch-feeding means 7 which feeds the workpieces (at a prescribed pitch) to the bonding head section 6, and a discharge means 8 which discharges the finished workpieces onto the main conveyor 2.
The workpieces to be supplied to the bonders are fed to the main conveyor 2 from a supply magazine 9. The workpieces which have been finished by the wire bonders 1A through 1D are discharged to return to the main conveyor 2 and then accommodated in a storage magazine 10.
More specifically, the workpieces from the supply magazine 9 are supplied to one of the wire bonders 1A through 1D (upon request from such a particular bonder) via the supply means 5 of such wire bonder. The workpieces on which wire bonding has been completed by the wire bonder are discharged and returned to the main conveyor 2 by the discharge means 8 and then accommodated in the storage magazine 10.
Thus, the supply and discharge of the workpieces are performed using the main conveyor 2 which is provided to be used commonly to a plurality of wire bonders 1A, 1B . . . .
Accordingly, it is necessary to establish synchronization among the wire bonders 1A through 1D (i.e., the processing devices) so that the discharge operation is performed in a unified manner (i.e., with a multiple number of workpieces being discharged simultaneously) using a prescribed timing which prevents any restriction on the supply of the workpieces. It is otherwise necessary to perform the supply and discharge so that the workpieces are supplied from and discharged onto the main conveyor 2 one workpiece at a time.
Thus, in prior art apparatus described above, it is necessary to establish a supply-discharge synchronization among the processing devices when many workpieces are conveyed by the main conveyor at the same time. As a result, there are limitations to the processing time of each processing device and to the number of devices to be installed. If the workpieces are conveyed by the main conveyor one workpiece at a time, the conveying efficiency of the line drops greatly as the number of processing devices increases.